Grounding wheel for grounding electrical devices

ABSTRACT

A toothed eccentric grounding wheel is freely rotatably supported on the conventional grounding screw of the safety grounding circuit of a grounding electrical device and is arranged upon its rotation in a predetermined direction along a noncircular path to cam with an inner portion of a grounded metal box. The wheel is provided with peripheral teeth which upon such camming of the wheel engage with and firmly dig into the end wall of the box such as to effect a high-pressure grounding contact between the grounding screw and the box.

ilnited States Patent Carissimi [54] GROUNDING WHEEL FOR GROUNDING ELECTRICAL DEVICES [72] Inventor:

[73] Assignee:

Conn.

[22] Filed:

July 13, 1970 211 Appl. No.: 54,514

Vincent L. Carissimi, Fairfield, Conn.

Harvey Hubbell, Incorporated, Bridgeport,

[ 1 Mar. 14, 1972 1,960,191 5/1934 Staub et al. ..339/274 X Primary Examiner-Marvin A. Champion Assistant Examiner-Robert A. Hafer AttrneyWooster, Davis & Cifelli 7] ABSTRACT A toothed eccentric grounding wheel is freely rotatably supported on the conventional grounding screw of the safety grounding circuit of a grounding electrical device and is arranged upon its rotation in a predetermined direction along a noncircular path to cam with an inner portion of a grounded metal box. The wheel is provided with peripheral teeth which upon such camming of the wheel engage with and firmly dig into the end wall of the box such as to effect a high-pressure grounding contact between the grounding screw and the box.

[56] References Cited 12 Claims, 5 Drawing Figures UNITED STATES PATENTS 3,503,032 3/1970 Routh et al ..339/14 R 16 M M M 42 l 1 i I l 12 GROUNDING WHEEL FOR GROUNDING ELECTRICAL DEVICES BACKGROUND OF THE INVENTION The present invention relates to an improved grounding connection for electrical devices, such as outlet receptacles, arranged to be grounded to a grounded metal wall box.

A common type of grounding electrical device, the outlet receptacle, customarily includes a pair of slots associated with female electrical contacts for receiving the line blades of a male plug and a third slot associated with a female grounding contact for receiving the grounding prong on the plug. One way of grounding such a receptacle to a grounded wall box is to electrically couple the female grounding contact to a mounting yoke which may be of the U-shaped type or the socalled straight-through type and which aside from mounting the device in the wall box also effects a grounding electrical contact between the safety grounding circuit of the receptacle and the box by the direct contact of the mounting yoke ears and lugs of the box, and mounting screws for connecting them. To satisfy safety requirements, special screw connections have been employed; however, they are costly and deficient. An alternative way of grounding the receptacle to the wall box is to ground the usual grounding screw on the mounting yoke to the wall box by an auxiliary grounding jumper. This type of grounding connection is uneconomical both as regards material and cost of installation involved.

SUMMARY OF THE INVENTION Accordingly, it is a primary object of the invention to provide simple, economical, novel and effective means for grounding a grounding electrical device to a wall box without employing an auxiliary grounding jumper or special mounting yoke earsbox lugs screw connections. It is another object to provide such grounding means that are easily attached to the device and placed into its grounding position after mounting of the device in the box.

The objects of the invention are achieved in one form by providing an eccentric metallic wheel freely rotatably supported on the grounding terminal screw of the safety grounding circuit of a grounding electrical device, which is arranged, upon its rotation in a predetermined direction, to cam into an inner portion of a grounded metal box, the wheel being provided with peripheral teeth which upon such camming of the wheel firmly dig into an inner wall portion of the box so as to effect a high-pressure grounding contact between the grounding screw and the box and prevent unintended back-off. In another form of the invention, means are provided for stabilizing the wheel on the electrical device to enhance its operation and permit use ofa minimum thickness wheel.

The manner in which the foregoing objects are achieved will be apparent from the following description, the appendent claims and the figures of the attached drawing wherein:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front view of an electrical outlet receptacle showing the grounding member of the invention applied thereto;

FIG. 2 is a side view of the device of FIG. I and illustrates the grounding member in inoperative position;

FIG. 3 is a side view of one end portion of the device of FIG. 2 and illustrates the grounding member as being placed into its grounding position;

FIG. 4 is an enlarged partial front view of the device of FIG. 1, partially broken away to illustrate the stabilizing means for the grounding member; and

FIG. 5 is a similar enlarged partial front view of the device of FIG. 1, partially broken away to illustrate a further embodiment of the stabilizing means for the grounding member.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention is shown as applied to a grounding duplex wall outlet receptacle, but may be applied to other electrical devices, such as switches, pilot lights, and the like. In the figures, in which like reference numerals index like parts, the grounding outlet receptacle 10 is seen to be mounted in a conventional metal outlet box I2 which, in turn, is to be groundingly mounted in a baseboard, panel, wall or the like.

As shown in FIGS. I and 2, the receptacle It) comprises the usual body of insulating material 14 which on its front surface is provided with faces 16, 18 each having a pair of entrance slots 20, 22 for insertion of the line blades of a male plug for engagement with receptacle female electrical contacts (not shown) mounted in the body 14 inwardly from the slots 20, 22. Each of the faces 16, 18 further includes a grounding opening 24 for insertion of the grounding prong on the male plug for engagement with receptacle female grounding contacts (not shown) in the body M inwards ofthe slots 24. Binding screws 26, 28, FIG. 2, are provided on the body M to establish the usual connection between the female electrical contacts in the body and the conductor wires of the house wiring system. The female grounding contacts are interconnected by suitable connector means such as for example a conven- ,ional internal electrically conductive bridging member shown in dashed lines in FIG. 1 and indicated by the reference numeral 30. This member 30 includes an angled lateral portion terminating at one side and adjacent one end of the body 14 in the usual wiring terminal plate 32 which is drilled and tapped to receive the usual binding or grounding screw 34. The female grounding contacts and the bridging member thus constitute a safety grounding circuit in the receptacle l0.

Novel grounding means is provided for grounding this safety circuit to a portion of the box 12. This grounding means comprises a toothed wheel 36 which is eccentrically freely rotatably supported on the grounding screw 34. To this end, the wheel 36 is provided with an inwardly extending socket or slot 38 having an innermost end (not shown) which is off center relative to the minor axis of the wheel and freely en gages the backed-out portion of the screw 34 extending through the wheel. The outer peripheral surface of the wheel is formed with a plurality of sharp-edged teeth 4M) inclined in counterclockwise direction and formed by a series of peripherally spaced shoulders and inclined curved surfaces connecting the bottom of each shoulder with the top of the next adjacent shoulder. This direction of inclination of the teeth is advantageous in that it permits positioning of the wheel onto the screw 34 after mounting of the receptacle in the box and, thereafter, adjustment of the wheel into operative position.

Mounting of the receptacle in the box is accomplished by means of a pair of connecting members, which may be part of any type mounting yoke. As illustrated, they are generally L- shaped connecting members 42, 44 each of which includes a first portion 46 secured to an end face of the body 14, and a second portion 48 angled relative to the first portion and secured in conventional manner to the mounting lugs 50 of the box by means of mounting screws 52.

Upon such mounting of the receptacle in the box, the wheel 36 is slipped over the shaft of the screw 34 and is initially placed in its inoperative position shown in FIG. 2, in which position the teeth are detached from the box. Subsequently, and as shown in FIG. 3, the wheel 36 is clockwise rotated from its inoperative position towards its grounding position. During such rotation, the wheel periphery describes a noncircular path until portions of such periphery cam with the inner adjacent end wall of the box, in which condition the teeth firmly dig into such end wall. Such rotation is accomplished by engaging the inclined teeth with an edged tool, such as the screwdriver of FIG. 3, and by pressing the teeth downwardly into engagement with the box surface. As a result of their thus established anchoring condition, the teeth resist the strains that tend to return them into their original or nonengaging state. To detach the teeth 42 from the box surface it is first necessary to remove or loosen the screws 52 and to shift the receptacle I0 longitudinally away from the end wall engaged by the teeth whereby to draw the latter out of engagement with this wall.

The eccentricity or cam design of the wheel 36 serves to allow for variations in distance between the grounding screw position and the end wall of the box such as to at all times ensure a positive grounding contact between the wheel and the box. Also, the cam design permits unrestricted assembly of the wheel and the grounding screw before tightening of the former against the end wall.

FIG. 4 shows the arrangement of FIG. 1, however, incor porating stabilizing means for stabilizing the wheel 36 on the body 14. This means is seen to include a pair of spaced shoulders S4, 56 integral with and projecting laterally outwardly from the body 14 into abutting engagement with lateral por tions of the wheel 36.

FIG. 5, in essence, shows the arrangement of FIG. 4, however, in this instance the wheel 36 is provided with a substantially U-shaped metallic stabilizing member 58. This member includes a base portion 60 fixedly embedded in the body 14, and spaced leg portions 62, 64 projecting laterally outwardly from the body into abutting engagement with lateral portions of the wheel. The base 60 is provided centrally with an opening 66 which engages the shank of the screw 34. If desired, when employing either type of full yoke, the metallic stabilizing leg portions may be formed integrally with or attached to the yoke.

The stabilizing members shown in the embodiments of FIGS. 4 and serve to provide greater lateral stability for the wheel 36 and are furthermore advantageous in that they permit the use of thinner material for the wheel.

It is believed that the many advantages of this invention will now be apparent to those skilled in the art. It is also believed that many variations and modifications will be apparent which do not depart from the spirit and scope of the invention. Accordingly, the foregoing description is to be construed as illustrative only, rather than limiting. This invention is limited only by the scope of the following claims.

What is claimed is:

1. In an electrical device arranged to be mounted in a grounded metal outlet box: a body of electrical insula,ing material; a plurality of electrical elements carried by said body; grounding means on said body, said grounding means including a grounding member rotatably supported on said body and having sharp-edged peripheral teeth at least some of which are arranged, lhen the device is mounted in the metal outlet box, to be selectively rotatably moved relative to said body into engagement with and dig into an inner wall of the box so as to effect high-pressure grounding contact between said rotatable member and the box.

2. The device as defined in claim 1, wherein said rotatable member is substantially annular and includes an outer peripheral surface, a plurality of peripherally spaced teeth provided on at least part of said surface, and an opening in said rotatable member for rotatably supporting the latter on support means on said body; said rotatable member being arranged to be moved on said support means from a position in which said teeth are detached from the said wall of the box to a position in which said teeth engage said wall.

3. The device as defined in claim 1, wherein said rotatable member is a toothed eccentric wheel member and comprises an outer peripheral surface having inclined teeth provided on at least part of said surface, and a slot extending inwardly from said surface and having an innermost end off-center relative to the minor axis of said wheel member and freely engaging sup port means on said body; said teeth being unidirectionally inclined in a direction opposite the direction of rotation of said rotatable member, the latter being arranged to be moved along a noncircular path from a position in which said teeth are detached from the said wall of the box to a position in which said teeth engage such wall.

4. The device as defined in claim 1, wherein said grounding means includes electrical conductor means carried in said body for grounding said plurality of electrical elements, said electrical conductor means defining an opening on one side of said body adjacent one end thereof, and wherein said grounding means further includes a conductive detachable binding member having an inner portion tightly received in said opening and having an outer portion freely supporting said rotatable member.

5. The device as defined in claim 1, including nonconductive stabilizing means on said body for stabilizing said rotatable member, said stabilizing means constituting at least one shoulder projecting laterally outwardly from said body into abutting engagement with lateral portions of said rotatable member.

6. The device as defined in claim 1, wherein said grounding means further includes stabilizing means for stabilizing said rotatable member on said body, said stabilizing means comprising a substantially U-shaped member having spaced leg portions projecting therefrom into abutting engagement with lateral portions of said rotatable member.

7. The device as defined in claim 6, wherein said U-shaped member is made of an electrically conductive material having a base portion that includes an opening for receiving support means for said rotatable member.

8. The device as defined in claim I, and including means for mounting said body in the metal box, said mounting means comprising a pair of connecting members each having a portion arranged to be secured to the box.

9. For use in effecting a grounding electrical connection between a grounding screw of an electrical device and a portion of a grounded metal outlet box, a grounding means comprising: a grounding member arranged to be rotatably mounted on the grounding screw and having sharpedged peripheral teeth arranged, when the device is mounted in the metal outlet box, to be selectively rotatably moved relative to the device into engagement with and dig into an inner wall of the box so as to effect high-pressure grounding contact between said rotatable member and the box.

10. The means as defined in claim 9, wherein said rotatable member is a toothed eccentric wheel member and comprises an outer peripheral surface having inclined teeth provided on at least part of said surface and a slot extending longitudinally inwardly from said surface and having an innermost end of?- center relative to the minor axis of said wheel member and arranged to freely slidably engage the grounding screw for supporting said wheel member on such screw; said teeth being unidirectionally inclined in one direction opposite the direction of rotation of said wheel, and arranged to be moved along a noncircular path from a position in which said teeth are disengaged from the wall of the box to a position in which at least some of said teeth engage such wall.

11. The combination defined in claim 9, which further comprises means for stabilizing said rotatable member on the device having a portion arranged to project therefrom into abutting engagement with lateral portions of said rotatable member.

l2. The combination defined in claim 11, wherein said stabilizing means is made of an electrically conductive material, and includes a portion having an opening arranged to receive the grounding screw. 

1. In an electrical device arranged to be mounted in a grounded metal outlet box: a body of electrical insulating material; a plurality of electrical elements carried by said body; grounding means on said body, said grounding means including a grounding member rotatably supported on said body and having sharp-edged peripheral teeth at least some of which are arranged, when the device is mounted in the metal outlet box, to be selectively rotatably moved relative to said body into engagement with and dig into an inner wall of the box so as to effect high-pressure grounding contact between said rotatable member and the box.
 2. The device as defined in claim 1, wherein said rotatable member is substantially annular and includes an outer peripheral surface, a plurality of peripherally spaced teeth provideD on at least part of said surface, and an opening in said rotatable member for rotatably supporting the latter on support means on said body; said rotatable member being arranged to be moved on said support means from a position in which said teeth are detached from the said wall of the box to a position in which said teeth engage said wall.
 3. The device as defined in claim 1, wherein said rotatable member is a toothed eccentric wheel member and comprises an outer peripheral surface having inclined teeth provided on at least part of said surface, and a slot extending inwardly from said surface and having an innermost end off-center relative to the minor axis of said wheel member and freely engaging support means on said body; said teeth being unidirectionally inclined in a direction opposite the direction of rotation of said rotatable member, the latter being arranged to be moved along a noncircular path from a position in which said teeth are detached from the said wall of the box to a position in which said teeth engage such wall.
 4. The device as defined in claim 1, wherein said grounding means includes electrical conductor means carried in said body for grounding said plurality of electrical elements, said electrical conductor means defining an opening on one side of said body adjacent one end thereof, and wherein said grounding means further includes a conductive detachable binding member having an inner portion tightly received in said opening and having an outer portion freely supporting said rotatable member.
 5. The device as defined in claim 1, including nonconductive stabilizing means on said body for stabilizing said rotatable member, said stabilizing means constituting at least one shoulder projecting laterally outwardly from said body into abutting engagement with lateral portions of said rotatable member.
 6. The device as defined in claim 1, wherein said grounding means further includes stabilizing means for stabilizing said rotatable member on said body, said stabilizing means comprising a substantially U-shaped member having spaced leg portions projecting therefrom into abutting engagement with lateral portions of said rotatable member.
 7. The device as defined in claim 6, wherein said U-shaped member is made of an electrically conductive material having a base portion that includes an opening for receiving support means for said rotatable member.
 8. The device as defined in claim 1, and including means for mounting said body in the metal box, said mounting means comprising a pair of connecting members each having a portion arranged to be secured to the box.
 9. For use in effecting a grounding electrical connection between a grounding screw of an electrical device and a portion of a grounded metal outlet box, a grounding means comprising: a grounding member arranged to be rotatably mounted on the grounding screw and having sharp-edged peripheral teeth arranged, when the device is mounted in the metal outlet box, to be selectively rotatably moved relative to the device into engagement with and dig into an inner wall of the box so as to effect high-pressure grounding contact between said rotatable member and the box.
 10. The means as defined in claim 9, wherein said rotatable member is a toothed eccentric wheel member and comprises an outer peripheral surface having inclined teeth provided on at least part of said surface and a slot extending longitudinally inwardly from said surface and having an innermost end off-center relative to the minor axis of said wheel member and arranged to freely slidably engage the grounding screw for supporting said wheel member on such screw; said teeth being unidirectionally inclined in one direction opposite the direction of rotation of said wheel, and arranged to be moved along a noncircular path from a position in which said teeth are disengaged from the wall of the box to a position in which at least some of said teeth engage such wall.
 11. The combination defined in claim 9, which further comPrises means for stabilizing said rotatable member on the device having a portion arranged to project therefrom into abutting engagement with lateral portions of said rotatable member.
 12. The combination defined in claim 11, wherein said stabilizing means is made of an electrically conductive material, and includes a portion having an opening arranged to receive the grounding screw. 